Cooperative intramolecular hydrogen bond and conformations of thiocalix[4]arene molecules

The joint FTIR spectroscopic study and ab initio quantum-chemical calculations (HF/3-21G and PBE/TZ2P methods) showed that thiocalix[4] arene molecules adopt the cone conformation in CCl₄ solutions. The weakening of the cooperative intramolecular H bond in thiocalix[4]arenes compared to the corresponding calix[4]arenes can be due to the larger thiocalixarene macrocycle, bifurcated hydrogen bond in it, and electron density transfer from the bridging S atom to the benzene ring.     

New preorganized calix[4]arenes. Part I. A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27,28-Dodecamethyl-5,11,17,23-tetrahydroxycalix[4] arene

A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27, 28-dodecamethyl-5,11,17, 23-tetrahydroxycalix[4]arene (1) have been prepared by reaction of appropriate oligoethylene glycol ditosylates with (1) in acetonitrile in the presence of potassium carbonate. A potassium template effect is observed during one of the double cyclizations.     

Synthesis of New Calix[4]arenes Functionalizated by Acetylhydrazide Groups

A series of new calix[4]phenols, calix[4]resorcinols and calix[4]pyrogallols with acetylhydrazide substitutes has been␣synthesized with high yields by hydrazinolysis of ester group containing calix[4]arenes. The synthesized calix[4]phenols adopt the cone conformation while the calix[4]resorcinol and calix[4]pyrogallol derivatives prefer the boat conformation. The amide fragment of the hydrazide groups predominantly exists in the trans-conformation. The binding ability of synthesized calix[4]arenes toward transition and alkali metals by solvent extraction has been investigated.     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.     

Evidence of Hydrogen Bonding in Stabilizing the Cone Conformation of a Monoalkylated Calix[4]arene. X-ray Structure of 25-[2-(ethoxy-1-p-toluene-sulfonate)phenyl]-26,27,28-trihydroxy calix[4]arene

The synthesis of25-[2-(ethoxy-1-p-toluene-sulfonate)phenyl]-26,27,28-trihydroxy calix[4]arene3 as a byproduct of the preparation of 1,3-dialkylated25,27-di-[2-(ethoxy-1p-toluene-sulfonate)phenyl]-26,28-dihydroxy calix[4]arene 2 is reported. Compound 3 is a monoalkylatedcalix[4]arene in the cone conformation. The X-ray structure of 3 showed that this conformation is stabilized by intramolecular hydrogen bonding.     

Ab initio studies of NMR chemical shifts for calix[4]arene and its derivatives

Ab initio calculations are performed for the calix[4]arene (1) and its derivatives (2 and 3), in this study. ¹H and ¹³C NMR measured spectral data given in our previous work are used to elucidate the structures of the prepared calix[4]arenes (1–3). The molecular geometry and chemical shift are calculated by using ab initio calculations based on the Hartree-Fock (HF) and the density functional theory (DFT) in the ground state. The results obtained from both methods are in agreement with the experimental results. The results of molecular geometry and chemical shifts show that DFT approach is closer to the experimental data than HF method.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

Photoactive Eu(III) and Tb(III) complexes of calix[4]arenes with pyridine-N-oxide pendant groups

Two calix[4]arenes with four 2-pyridyhnethyl-l-oxide pendant groups at the lower rim have been synthesized, and their Tb(III) and Eu(III) complexes are fluorescent upon UV light excitation at 312 nm. The complexes are not stable in aqueous solution, completely losing their luminescent properties.     

新型杯[4]席夫碱的合成及光致变色性质研究

合成了三种新型含杯[4]芳烃的席夫碱类化合物及不含杯[4]芳烃空腔的模型化合物, 利用IR, 1H NMR, 13C NMR, MALDI-TOF MS和元素分析对其结构进行了表征. 研究了它们的光致变色性能及杯[4]芳烃空腔、取代基和溶剂对光致变色性能的影响. 结果表明, 杯[4]芳烃、取代基OCH3和CH2Cl2可以改善席夫碱的光致变色性能.     

Polymeric membrane sodium-selective electrodes based on calix[4]arene ionophores

Six kinds of tetra alkylester type calix[4]arene derivatives, (R₁=R₂=CH₃1, C₂H₅2, C₃H₇3,n-C₄H₉4,t-C₄H₉5,n-C₁₀H₂₁6), a diethyl-didecyl mixed ester type (R₁=C₂H₅, R₂ =C₁₀H₂₁7), and three kinds of lower rim bridged types (R₁=C₂H₅, R₂–R₂=(CH₂)₁₀8, (CH₂)₁₂9, (CH₂)₂(OCH₂CH₂)₃10) were characterized by electrochemical measurement to elucidate the effect of the length of the alkyl group of alkoxycarbonyl substituents on Na⁺ selectivity. To obtain excellent Na⁺ selective ionophores, introduction of short chain alkyl groups rather than long chain ones, such as a decyl group, and maintenance of sufficient solubility of the calix[4]arene derivatives in the membrane solvent are required concurrently. Among the calix[4]arenes tested, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcalix[4]arene2, and the diethyl-didecyl mixed ester type derivative7 are the best ionophores for a Na⁺ selective electrode. On the other hand, sodium selectivity of the bridged type derivative9 is comparable or even superior to that of the known bis(12-crown-4).This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Isolation and X-ray crystal structure of a stable calix[4]arene monohemiketal

The formation of a stable calix[4]arene monohemiketal is described. X-ray crystallographic data provide conclusive evidence for the presence of a stabilizing hydrogen bond. Supplementary Data. Lists of H-atom parameters and bond lengths and angles involving hydrogens have been deposited with the British Library Document Supply Centre as Supplementary Publication No. SUP 82159 (5 pp.).     

New Tetrafunctionalized Cone Calix[4]arenes as Neutral Hosts for Anion Recognition

Abstract

The synthesis and anion binding properties of several new cone calix[4]arenes having different flexibility and tetrafunctionalized at the upper rim with various type of hydrogen bonding donor groups such as thioureas (1–3), trifluoroacetamides (4, 5) and perfluorinated alcohols (6) are reported. The results obtained show that thiourea receptors are the most effective in the complexation of all anions and that the rigid cone compound 2 is more efficient than the mobile cone analog 1 in the binding of spherical anions, whereas the reverse is true for the complexation of tetrahedral H₂PO₄ ^? anion.     

Highly selective fluorescent recognition of amino alcohol based on chiral calix[4]arenes bearing L-tryptophan unit

Four two-armed chiral calix[4]arenes (1a–1d) functionalised at the lower ring with amino acid units have been synthesised and the structures of these compounds were characterised by IR, MS, ¹H NMR, ¹³C NMR spectra and elemental analysis. Their molecular recognition abilities towards amino alcohol were examined by fluorescence titration experiment in three kinds of solution. The results indicated that these receptors exhibited excellent fluorescent response to phenylglycinol and could distinguish phenylglycinol from phenylalaninol rapidly through the obvious difference in the fluorescent response. Solvent comparative experiments also indicated that acetonitrile was the best solvent to detect these phenomena.     

Theoretical study on conformational features and cation-binding properties of a diquinone calix[4]arene

Theoretical studies of a diquinone calix[4]arene and its interactions with the cations Li⁺, Na⁺, K⁺ and Ag⁺ have been performed. Conformational features and cation-binding properties were evaluated with the restricted hybrid Becke three-parameter exchange functional method using the 6-31G(d) basis set and its relativistic effective core potentials. To model the effect of medium, the polarisable continuum model was also used. Four typical conformations of the parent diquinone calix[4]arene were studied. The calculated results show that the most stable conformers are 1,3-alternate and partial cone in the gas phase and in CH₂Cl₂ solution, respectively. The optimised geometric structures were used to perform natural bond orbital analysis. The two main types of driving force metal–ligand and cation–π interactions are investigated. The calculated binding energy for cations (Li⁺, Na⁺, K⁺ and Ag⁺) is discussed. The calculated results indicate that cone complexes are the most stable.     

Studies on the syntheses and properties of boronoalkoxy calix [ 4 ] arenes

New boronoalkoxycalix[4]arenes were synthesized by allylation, alkylation, hydroboration and hydrolysis of 25,26,27,28-tetrahydroxycalix[4]arene, and identified by elemental analysis, IR, 1H NMR, 13C NMR, 11B NMR, MS and UV spectra. The data of UV and fluorescence spectra showed that tctrapropoxycalix-[4]arene triboronic acid could coordinate significantly with monosaccharides.     

Synthesis and evaluation of neutral anion receptors based on acylhydrazide-appended calix[4]arenes

A new class of neutral receptors based upon acylhydrazide-appended calix[4]arenes was synthesised and evaluated for recognition of anions. Detailed NMR and single-crystal X-ray analyses of one of the synthesised compounds reveal that anion recognition in such derivatives is achieved through cooperative hydrogen bond interactions. The presence of three centred NH–O and two OH–O hydrogen bonds at the lower rim of the synthesised calixarene architecture apparently helps the molecular scaffold to retain cone conformation to enable deployment of intermolecular hydrogen bonds for selective recognition of HSO₄ ^? ion in preference to F^?, Cl^?, Br^?, I^?, ClO₄ ^?, AcO^? and PF₆ ^? ions.     

Synthesis and binding studies of novel bisthiacalix[4]arenes with diimime linkages

A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions.     

Synthesis and Conformational Properties of Bis（calix [4] arene）

The bis(calix [4] arene)3 was synthesized in moderate yield by the reaction of p-tert-butylcalix [4] arene (1) with 1,4-bis(chloromethyl) benzene (2). The conformation of all alkylated product 4 was investigated by the variable-temperature ^1H-NMR.